The present invention is related to a method for applying a sealing compound to a surface, preferably into a closure cap for containers.
Closure caps for containers, glasses or similar containers mostly have a seal in the interior of the bottom, in order to seal the container content sufficiently with respect to the atmosphere.
It is known to incorporate such seals in the form of sealing compounds, preferably in ring shape. It is known to use PVC as a material for this, which is provided with a plasticizer for reasons of process technology and for purposes of sealing. However, plasticizers have the property to escape from the PVC to a certain extent. This is increasingly disapproved or officially forbidden for reasons of health and environment. PVC is applied at 40-65° C. in liquid form by way of an injection nozzle.
If another plastic material like TPE, for example, is used instead of PVC, the plastic material for such seals is plasticized in a suitable way at first, and then the melt is applied into the interior of the cap with the aid of a suitable device. Such a device has become known from EP 1 527 864. It has an outer, sleeve-shaped and height-movable stamp, in which is situated an inner height-movable stamp. A ring-slide slides on the outer side of the outer stamp, which separates an extrudate off from injection nozzles when it is shifted into a lower position, so that the extrudate is discharged into the ring space between a ring having the nozzle openings and the outer stamp. The extrudate is pressed against the inner bottom of the cap with the aid of the outer slide, wherein the ring slide and the inner stamp rest on the bottom and limit a ring-shaped moulding cavity by doing so. Disadvantageous in the known device are the imprecise portioning of the sealing material, the not uniform ring shape of the extrudate and the problem to cool the outer slide in the hot environment.
All approaches of a solution, as well as the patent described above, are affected by the great danger that the hot sealing compound adheres on surfaces that are not cold. This effect is per se known and is usually almost overcome by cooling the surfaces on which adherences are to be avoided. This problem also occurs with the known applicator and also with other applicators. The reason for this is that it is not possible to technically realise temperature differences of about 180° C. on a very narrow space.
Thus, the present invention is based on the objective to provide a method for annularly applying a sealing compound to a surface, into a closure cap for containers in particular, by which the sealing compound can be effectively discharged without that adherences or draw of thread occurs on outer surfaces of the applicator.